This invention relates to air sampling systems and more particularly to methods and apparatus for removing amine compounds from air samples.
Devices and methods are known for sampling air to identify types and levels of amine compounds present in the environment. These compounds may arise from a variety of sources, such as the manufacture and use of chemicals, combustion of fuels, and others. The conventional method for extraction of airborne amine compounds requires the air sample to pass over a bed of silica gel to trap the amines therein. Following this first step, the silica gel is then washed with a solution of 0.2 N sulfuric acid in 10% methanol to remove the trapped amine compounds. The resultant wash may then be gas chromatographically separated into its constituent amine compounds. This method, however, is generally ineffective for air samples which include oxides of nitrogen. More particularly oxides of nitrogen (for example NO, N.sub.2 O.sub.3 and N.sub.2 O.sub.4) may readily undergo a gas phase N-nitrosation reaction with the amines trapped on the silica gel. Consequently, the analysis of the amine-containing wash results in errors due to the amines which have been nitrosated. As a result "detected" amine compounds do not include the amines from the original sample which have been converted to N-nitroso compounds by N-nitrosation during the collection and analysis process. Consequently, an accurate air sampling and amine compound detection system must be effective in atmospheres in which reactive compounds are present in large concentrations.
Accordingly, it is a general object of this invention to provide improved methods and apparatus for removing amine compounds from air.
It is another particular object of the invention to provide an improved method and apparatus for determining the concentration of amine compounds in an air sample without formation of nitrosamines from amines in the sample.
It is also an object of the invention to provide apparatus for collecting amine compounds from air which is compact, inexpensive, portable, and simple to use.